44 



This comparison shows how incorrect it is to suppose that in 

 consequence of the diminution of the vital phenomena in cold wea- 

 ther, a batrachian that lives several months does not live more 

 than another living only several hours in summer. 



This opinion is also proved erroneous by the facts which I have 

 already related, and which show that all the functions and vital 

 properties existing in frogs deprived of their medulla oblongata, 

 appear to be as active as in unmutilated frogs. No doubt that 

 there is a notable difference between summer and winter as to the 

 activity of vital phenomena in frogs, but if we suppose that these 

 phenomena are in winter only the tenth of what they are in 

 summer, and if we consider, consequently, the duration of life in 

 winter as being only the tenth of what it is, we shall have, 

 nevertheless, a duration in winter forty or fifty times as great as 

 the duration in summer. 



V. Now I have to examine why, in summer, the life of cold- 

 blooded vertebrata, deprived of the medulla oblongata, is much 

 shorter than in winter. 



The principal cause of this difference is in the fact that the 

 cutaneous respiration, (it is known that the pulmonary respira- 

 tion does not exist in animals deprived of the medulla oblon- 

 gata,) which is sufficient as long as the temperature is very low, 

 becomes more and more insufficient, when the temperature be- 

 comes more and more elevated. So that the same law exists for 

 the cold-blooded vertebrata deprived of their medulla oblongata, 

 and for those which are not mutilated. The following experi- 

 ments concur to demonstrate the correctness of this view : 



I have found that frogs deprived of their medulla oblongata 

 live much longer when placed in oxygen than in atmospheric air. 

 I have made two series of experiments one in June, 1847, the 

 other in July, 1850. In both series the frogs were put imme- 

 diately after the operation, under a receiver full of oxygen. They 

 lived from eight to fourteen days at a temperature at which 

 life, in atmospheric air, is always shorter than six hours. The 

 temperature was from 64* to 84 F. (18 to 29 Cs.) These 

 frogs would have lived longer if the quantity of oxygen had 

 been more considerable. 



By pulmonary insufflation I have maintained life in tortoises 

 deprived of the medulla oblongata, much longer than when in- 



